Sure, that would work too. If you have to order the new R1 resistors anyway, a different LED doesn't seem to be as problematic.
Followers and Quickie
- Thread starter Jamier
- Start date
I really don’t want to screw with my Crack as it is dead quiet and works flawlessly. I was thinking about building one dedicated for this purpose ( of driving the MoFos ). I noticed the Mainline is on sale. What is the V swing of it? At 999.00 it seems like one hell of a deal.
Jamie
Jamie
On the "High" setting, there is enough voltage for your follower amp in the low power version, but not quite enough to drive the full power configuration all the way. The Mainline is a very popular kit for this specific application.
D
Deke609
Guest
Jamie - I picked up a couple of "Silent Wings 3" 140mm fans (non PWM) that run on anything from 5VDC to 12 VDC. At full power (12 VDC) they are spec'ed as max 15.5 dB(A). I tested one last night at full power and could barely hear it operate when it was held in in my hand in the open. At 9V I couldn't hear it at all.
And I just have to ask: "cavitation"? ??? I looked it up and still can't make sense of it - something to do with pockets of pressure drops caused by turbulence?
cheers, Derek
And I just have to ask: "cavitation"? ??? I looked it up and still can't make sense of it - something to do with pockets of pressure drops caused by turbulence?
cheers, Derek
Derek,
What is the CFM rating? Not that I know what CFM rating I need but it will give me some reference point to start with. Cavitation,as I know it, is the disorderly flow of air or liquid when it does not move smoothly through a pathway (i.e. the openings in the bottom of my chassis) thus, resulting in noise. I don't generally like fan cooled amps as everyone I have ever had could be heard. But, I think PB is right on this one. If I don't use a fan I will need to use an even larger heatsink and the one I have now is already pretty big. It is quite astounding how much heat one MOSFET can produce.
Jamie
What is the CFM rating? Not that I know what CFM rating I need but it will give me some reference point to start with. Cavitation,as I know it, is the disorderly flow of air or liquid when it does not move smoothly through a pathway (i.e. the openings in the bottom of my chassis) thus, resulting in noise. I don't generally like fan cooled amps as everyone I have ever had could be heard. But, I think PB is right on this one. If I don't use a fan I will need to use an even larger heatsink and the one I have now is already pretty big. It is quite astounding how much heat one MOSFET can produce.
Jamie
D
Deke609
Guest
[Edit: Correction! Mixing up my specs: 100 CFM @ 1000 RPM - 1000 CFM would be insane]
1000 CFM at max. The heatsink datasheets I looked at all dealt in feet per minute or second, or some such - don't remember. But there are online calculators for converting CFM to the unit of measurement you need for using datasheets to estimate the additional cooling effect you'll get from forced air.
You might also consider using a small fan - e.g., 40 cm and installing it so that blows directly against the long side of the heatsink at issue. There's a guy of DiyAudio - nikosokey - who did this and reports good results.
cheers, Derek
You might also consider using a small fan - e.g., 40 cm and installing it so that blows directly against the long side of the heatsink at issue. There's a guy of DiyAudio - nikosokey - who did this and reports good results.
cheers, Derek
Doc,
Thanks for that update, but PB is saying that the Mainline won’t quite drive the big MoFo version. Is there a mod, like the one he was suggesting for the Crack, that will increase the V swing without severely altering the character of the amp. I would not want to change an amp like a Mainline, irreversibly, anyway.
Jamie
Thanks for that update, but PB is saying that the Mainline won’t quite drive the big MoFo version. Is there a mod, like the one he was suggesting for the Crack, that will increase the V swing without severely altering the character of the amp. I would not want to change an amp like a Mainline, irreversibly, anyway.
Jamie
The F4 is usually the companion product paired with the Mainline as a power amp buffer.
I think you'd make about 14W. Have you evaluated the realistic power handling of the speakers you're using?
I think you'd make about 14W. Have you evaluated the realistic power handling of the speakers you're using?
PB, I use speakers that are mostly built by myself. Most of these operate well, outside of that figure. I listen semi nearfield so large output is not needed but the 20W rating associated with the big MoFo would be great for some of them. Several of these speakers are designed around 7 inch Seas midwoofers which do have good thermal compression and power handling capabilities. One of my dilemmas about the MoFo is how to increase the Current in order to drive the 4 ohm MTMs that I made designed around Seas ER 18s. I’m wondering if using the 193V inductor will accomplish this goal.
Jamie
Jamie
Increasing the power supply voltage isn't going to help with 4 ohm speakers. Increasing the idle current as much as possible would be a good idea, which would mean the beefier chokes and the same power supply. The 2.5A limit implied in the article will be your limiting factor, not the swing from the Mainline.
You could also investigate paralleling pairs of boards to increase current availability.
You could also investigate paralleling pairs of boards to increase current availability.
Basically the whole DC rail appears across the fet, so you multiply that by your idle current and you get dissipation.
If you go from 12V DC to 24V DC at the same bias current, then you double the dissipation through the fet.
If you go from 12V DC 1.25A to 12V DC 2.5A, then you also double the dissipation through the fet.
If you go from 12V DC 1.25A to 24V DC 2.5A, then you quadruple the dissipation through the fet.
If you go from 12V DC to 24V DC at the same bias current, then you double the dissipation through the fet.
If you go from 12V DC 1.25A to 12V DC 2.5A, then you also double the dissipation through the fet.
If you go from 12V DC 1.25A to 24V DC 2.5A, then you quadruple the dissipation through the fet.
Also note that my power estimates are presuming that whatever voltage coming into the amp can be swung successfully by the MoFo. Personally I would use the 193V if your budget allows.
